The present invention is directed to a manually operated chipping tool for removing material from a surface using several needle-type chisels or cutters and a housing containing a needle cage, an anvil indirectly abutting against the housing through a compression spring, and a hammer for striking the anvil, all arranged to move parallel to the axial extent of the needle type chisels. The needle cage has a plurality of bores through which the needle-type chisels extend.
Manually operated tools for removing material from a surface or for machining a surface are known. These known manually-operated tools include a housing in which a striking mechanism and an axially displaceable needle cage are arranged. The needle cage has a number of bores through which the needle-type chisels or cutters extend and project outwardly from the housing.
The striking mechanisms in these known manually operated tools can be placed in motion by different media, in particular such as compressed air and liquid. A hammer of the striking mechanism applies blows to an anvil which, in turn, directs blows against the needle-type chisels. Considerable heating is produced in the bores of the needle cage in the region of the needle heads during the axial displacement of the needle-type chisels.
Since the operating media penetrates at least partially into the manually operated tool when it is operated, the parts located within the housing are cooled, so that damage to the needle-type chisels in the region of the needle heads or the needle cage is avoided.
A manually operated tool is disclosed in DE-PS 34 17 735 in which a number of needle type chisels are arranged next to one another in a parallel manner in a needle cage displaceable in a housing. The cage is provided with bores through which the needle-type chisels extend. A compression spring located in the housing presses against an edge or margin of the needle cage and presses it against an anvil. A reciprocating motion of the anvil is achieved by a reciprocating hammer which is part of a striking mechanism powered by an electric drive motor. The drive motor is supported in the housing of the manually operated chisel and is controlled by an actuation switch located in the region of a handle. The needle-type chisels are axially displaceable in the bores extending through the needle cage. The axial displacement of the chisels is obtained by the anvil located behind the needle-type chisels and displaced relative to them in an axially parallel manner, so that when the anvil is driven it strikes against the needle heads of the needle-type chisels.
During the operation of the tool, the needle-type chisels are pressed against the surface of a work piece, whereby the needle-type chisels are displaced axially relative to the needle cage in the rear end direction of the tool until the needle heads of the chisels come to rest at the anvil. When the drive motor is operated, blows are directed from the striking mechanism to the hammer which transmits such striking action against the anvil, whereby the needle-type chisels are driven in the forward direction at a very high speed and upon contacting the surface being worked on rebound in the axial direction. This axial displacement of the needle-type chisels occurs very rapidly, so that high friction is generated between the chisels and the bores through the needle cage. This reaction heats the needle cage and the chisels to a very considerable extent and entails damage to the needle cage and the chisels.
In this known manually operated tool, the striking mechanism also generates heat when the tool is operated which heat is generated in particular by the compression of air and such heat can not be dissipated at the rate at which it is generated. Accordingly, such heat generated within the manually operated tool causes an additional heating of the anvil, the needle cage and the needle-type chisels and further promotes the above-mentioned damage.